1. Field of the Invention
The present invention relates to an image recording apparatus and an image recording method which record an image on an elongated strip-shaped recording medium while transporting the recording medium.
2. Description of the Background Art
An inkjet image recording apparatus which records an image on elongated strip-shaped printing paper by ejecting ink from a plurality of recording heads while transporting the printing paper has heretofore been known. In the image recording apparatus of this type, inks of different colors are ejected from the respective recording heads. A multicolor image is recorded on a surface of the printing paper by superimposing single-color images formed by the respective color inks. The image recording apparatus of this type includes a detection mechanism for detecting a widthwise position (position as seen in a width direction) of the printing paper at all times for the purpose of controlling the position of ejection of ink with respect to the printing paper.
Such a conventional image recording apparatus including the detection mechanism is disclosed, for example, in Japanese Patent Application Laid-Open No. 2008-155628 and Japanese Patent Application Laid-Open No. 2003-182896. The apparatus disclosed in Japanese Patent Application Laid-Open No. 2008-155628 uses a plurality of line image sensors to detect the angle of skew of a recording medium, thereby adjusting the timing of ink ejection in accordance with the detected angle of skew (with reference to claims 1 and 2 and FIG. 1). The apparatus disclosed in Japanese Patent Application Laid-Open No. 2003-182896 includes two or more sensors for detecting edges of paper, and feeds a difference between outputs from the sensors where a constant time difference is established back to a correcting part (with reference to claim 1 and FIG. 1).
Unfortunately, the image recording positions of the recording heads and the detection positions of the sensors are different on a transport path of the printing paper in the apparatuses disclosed in Japanese Patent Application Laid-Open No. 2008-155628 and Japanese Patent Application Laid-Open No. 2003-182896. In the configurations of these apparatuses, the widthwise position of the printing paper in the recording position accordingly does not precisely coincide with the detection result obtained from each sensor. For recording of an image of higher quality, it is necessary to identify the widthwise position of the printing paper in the image recording position. However, the recording heads are disposed in the recording positions of the printing paper. For this reason, it is often difficult in terms of space to place the sensors in addition to the recording heads in the recording positions. In particular, the space for the placement of the sensors is more limited in an apparatus which records an image across the full width of printing paper.